import doctest

def average(values):
    """Computes the arithmetic mean of a list of numbers.
    >>> print(average([20, 30, 70]))
    40.0
    """
    return sum(values) / len(values)

def add(v1, v2):
    return v1 + v2

doctest.testmod()   # 自动验证嵌入测试.

